Mega Gyarados as a check.
Gyarados @ Gyaradosite
Ability: Intimidate
EVs: 252 Atk / 4 Def / 252 Spe
Jolly Nature
- Dragon Dance
- Crunch
- Waterfall
- Earthquake
Gyarados needs a free switch to come in, but when it does, Intimidate is a godsend, allowing it a setup turn (assuming it comes in in normal form). +1 EQ is a roll to OHKO after rocks, but if it's not safe to set up, it's still a clean two-shot at +0.

Gyarados @ Gyaradosite
Ability: Intimidate
EVs: 252 Atk / 4 Def / 252 Spe
Jolly Nature
- Dragon Dance
- Crunch
- Waterfall
- Earthquake
Gyarados needs a free switch to come in, but when it does, Intimidate is a godsend, allowing it a setup turn (assuming it comes in in normal form). +1 EQ is a roll to OHKO after rocks, but if it's not safe to set up, it's still a clean two-shot at +0.
-1 252 Atk Choice Band Adaptability Crawdaunt Crunch vs. 0 HP / 4 Def Mega Gyarados: 77-91 (23.2 - 27.4%)
-1 252 Atk Choice Band Adaptability Crawdaunt Crabhammer vs. 0 HP / 4 Def Mega Gyarados: 96-113 (29 - 34.1%)
Without Intimidate (coming in as mega, double switch, etc.):
252 Atk Choice Band Adaptability Crawdaunt Crunch vs. 0 HP / 4 Def Mega Gyarados: 114-135 (34.4 - 40.7%)
252 Atk Choice Band Adaptability Crawdaunt Crabhammer vs. 0 HP / 4 Def Mega Gyarados: 143-169 (43.2 - 51%)
252 Atk Mold Breaker Mega Gyarados Earthquake vs. 0 HP / 4 Def Crawdaunt: 141-167 (52.8 - 62.5%)
+1 252 Atk Mold Breaker Mega Gyarados Earthquake vs. 0 HP / 4 Def Crawdaunt: 212-250 (79.4 - 93.6%)
-1 252 Atk Choice Band Adaptability Crawdaunt Crabhammer vs. 0 HP / 4 Def Mega Gyarados: 96-113 (29 - 34.1%)
Without Intimidate (coming in as mega, double switch, etc.):
252 Atk Choice Band Adaptability Crawdaunt Crunch vs. 0 HP / 4 Def Mega Gyarados: 114-135 (34.4 - 40.7%)
252 Atk Choice Band Adaptability Crawdaunt Crabhammer vs. 0 HP / 4 Def Mega Gyarados: 143-169 (43.2 - 51%)
252 Atk Mold Breaker Mega Gyarados Earthquake vs. 0 HP / 4 Def Crawdaunt: 141-167 (52.8 - 62.5%)
+1 252 Atk Mold Breaker Mega Gyarados Earthquake vs. 0 HP / 4 Def Crawdaunt: 212-250 (79.4 - 93.6%)